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THE ECONOMIC STATUS OF INSECTS 

AS A CLASS. 



By L O; HOWARD. 



Address of the Eetieing Peesident of the Biological Society 
OF Washington, Deliveeed January 18, 1899. 



[Beprinted from SCIENCE, N. S., Vol IX., No. S16, Pages S33-i^7, 
February 17, 1899. } 






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D. of u, 



iReprinted from SCIENCE, N. S., Vol. IX., No. 216, 
Pages 233-U'^, February 17, 1899. '\ 



THE ECONOMIC STATUS OF INSECTS AS A 
CLASS."^ 

The popular conception of insects in gen- 
eral is undoubtedly that they are injurious. 
Many writers, it is true, have pointed out 
the benefits derived from insects, but we 
think of their damage to crops and of their 
annoyance to man and animals, and this as- 
pect of the subject is at once apt to prepon- 
derate in our minds. It is more than 80 
years since Kirby and Spence contrasted 
the injuries caused by insects with the bene- 
fits derived from them, and it has not l>een 
comprehensively done since. In the mean- 
time, whole groups of important injuries 
have been developed and whole classes of 
beneficial work have been discovered. 
Moreover, the tendency of modern thought 
has not taken this direction. The biologic 
taxonomic and phylogenetic, and other as- 
pects of large groups of forms of life have 
been considered to the exclusion of the eco- 
nomic aspect, and even where this side has 
attracted attention investigators have con- 
fined themselves to specific problems and 
have not generalized. It may be interest- 
ing, therefore, once more to contrast the in- 
jurious insects with the beneficial ones in an 
effort to gain a clearer idea of the status of 
the group in its relations with man. 

In abroad way, we may consider the sub- 
ject under the following heads : 

* Address of the retiring President of the Biological 
Society of Washington, delivered January 18, 1899. 



2" 



Insects are injurious : 

1. As destroyers of crops and other val-- 
uable plant life. 

2. As destroyers of stored foods, dwell- 
ings, clothes, books, etc. 

3. As injuring live stock and other useful 
animals. 

4. As annoying man. 

5. As carriers of disease. 
Insects are beneficial : 

1. As destroyers of injurious insects. 

2. As destroyers of noxious plants. 

3. As pollenizers of plants. 

4. As scavengers. 

5. As makers of soil. 

6. As food (both for man and for poultry,, 
song birds and food fishes) and as clothings 
and as used in the arts. 

DESTROYERS OF CROPS AND OTHER USEFUL 
PLANTS. 

In the present balance of nature one of 
the chief functions of insect life is to keep 
down superabundant vegetation. Almost 
every kind of plant has its insect enemies, 
and has had such enemies for many thous- 
ands of years. So soon as man began to 
make an effort to upset nature's balance by 
cultivating certain plants at the expense of 
others he encountered nature's opposition 
by means of the increase of insect enemies 
of the particular plant cultivated, and al- 
most as early as there is any record of agri- 
culture in literature there is also mention 
of the destruction to crops caused by insects. 
Witness the writings of the prophet Joel^ 
who might almost be termed an agricul- 
tural pessimist. 

At the present time almost every culti- 
vated crop has not only its thousands upon 



tTiousands of individual insect enemies, but 
it is affected by scores and even hundreds of 
species. A mere tabulation of the insect 
enemies of the apple already recognized in 
this country shows 281 species, of clover 82 
species, and of so new a crop as the sugar 
beet 70 species. The insects of the vine, of 
the orange, of the wheat crop, and, in fact, 
of all of our prominent staples, show equallj' 
startling figures. 

The actual damage which is done by in- 
sects in this way is difficult to express. 
Many attempts have been made by writers 
on economic entomology to express it in 
money values. For example, it was esti- 
mated by the late Professor Rilej' that the 
average annual damage to cultivated crops 
by injurious insects in the United States 
amounted to three hundred millions of dol- 
lars. The loss from the ravages of one 
species alone, the chinch bug, during one 
year was estimated at sixty millions of 
dollars. While it is true that the combined 
losses of individual growers might reach 
such enormous sums as these, there is an 
element in the total loss which we must 
not fail to take into consideration, and that 
is the enhanced value of the portion of the 
crop which remains. Even in tlie case of 
an individual a man may lose, for example, 
half of his crop through the work of the 
chinch bug, and yet, through widespread 
damage b}' this insect, the money value of 
the portion harvested may reach an amount 
almost as great as would have been gained 
through the low prices of a successful year 
of no insect damage As this applies to an 
individual, it applies much more stronglj^^ 
to a State or to the country at large, so that 
even in the year when the grain crop of 



the country was said to liave been damaged 
to the extent of sixty millions of dollars 
it is safe to say that the total price gained 
for the crop was as great as it would other- 
wise have been. These estimates of dam- 
age, therefore, would much better be ex- 
pressed in terms of bushels, or some other 
measure, than in money value. 

It is this aspect of our subject, the dam- 
age done by injurious insects to agriculture, 
that has given rise to the comparatively 
new branch of applied science which we 
now know as economic entomology, and 
which, although originating in Europe, has 
been encouraged to such an extent in our 
own country, owing partly to our greater 
necessities and partly to our practical turn 
of mind, that it is safe to say that at present 
America leads the rest of the world in this 
direction. 

It is undoubtedly true that this enormous 
injury to crops is the chief item in a general 
consideration of the injuries brought about 
by insects. 

AS DESTROYERS OF STORED FOODS, DWELLINGS, 
CLOTHES, BOOKS, ETC. 

It is safe to say that there is hardly any 
product of man's ingenuity, hardly one of 
the thousands of useful materials upon 
which depend his comfort and happiness, 
which is not damaged, directly or indirectly, 
by insects. The timbers of which his 
dwellings are built, nearly all of his house- 
hold utensils, his garments, practically 
everything which he uses as food, many of 
the liquids used as drink, his books, the 
ornaments with which he surrounds himself, 
the medicines which he takes when sick, 
the very tobacco with which he solaces him- 



■self— all are destroyed or injuriously af- 
fected by insects. There is, perhaps, one 
group of exceptions, and that is those articles 
which are composed wholly of metal, and 
yet even here insects may occasionally play 
an injurious part, since instances are on 
record of the destruction of lead pipes by 
insect larvaj, and the perforation of the 
metal linings of water tanks by small 
beetles. 

Such injuries to human products are more 
frequent and serious in tropical regions than 
in temperate zones, but even here insects 
of this nature cause very serious inconven- 
ience and great annual loss. It will answer 
our purpose, perhaps, to list some of the 
varying substances which are damaged in 
this way, to get an ideaof their almost uni- 
versal character: Ham, cheese, salted 
fish, butter, lard, dried mushiooms, rye 
bread, sweetmeats and preserves, powdered 
coffee, almonds and other nuts, raisins, 
breakfast foods, chocolate, ginger, rhubarb, 
black pepper, vinegar, sugar, wines, canned 
soups, tobacco, snuff, licorice, peppermint, 
aromatic cardamon, aniseed, aconite, bella- 
donna, musk, opium, ginseng, chamomile, 
boneset, hides, shoes, gloves and other 
leather articles, furniture, carpets, drawings 
and paintings, paint brushes, gun wads, 
combs, etc., made of horn ; bay, oats, straw, 
willow baskets, ax handles, ladders, wheel 
spokes and all sorts of agriculural imple- 
ments with wooden handles, barrels, wine 
casks, corks of wine bottles, sheets of cork, 
natural history collections, including skele- 
tons and mummies, and even Persian insect 
powder ! The mention of this well-known 
insecticide reminds one of the latest discov- 
ery, which is that certain flies in California 



breed in the crude petroleum pools in the 
vicinity of oil wells, a fact which is almost 
paradoxical in view of the extensive use of 
petroleum as an insecticide. 

AS INJURIOUS TO LIVE STOCK AND OTHER 
USEFUL ANIMALS. 

Every species of animal which has be- 
eome domesticated and is of value to man 
possesses its insect parasites and enemies. 
These in manj^ cases are the same specie& 
which aifect man and which we will men- 
tion in the next section ; others are specific 
to the animals or groups of animals which 
they affect. Horses, cattle, sheep, all 
possess insect enemies which are not only 
very deleterious to their health, but fre- 
quently cause their death in numbers. 

The disgusting bot fly of the horse, whose 
maggots live in incredible numbers in the 
stomach and intestines of this noble friend 
of the human race ; the bot fly of the ox, 
which causes innumerable sores on the 
backs of cattle and by its perforations ruins 
their hides for commercial use ; the bot fly 
of the sheep, which inhabits the nasal and 
orbital sinuses of the sheep and produces 
insanity and death — ^will instantly be re- 
called by those who are familiar with stock 
raising, while hundreds of other species^ 
some in no less degree, as the horn fly, the 
numerous gad flies, including the Tsetse fly 
of Africa, the screw worm fly of our South- 
western country, unite to make the lives of 
domestic animals a burden to themselves 
and a trial and a loss to their owners. 

An interesting attempt was made some 
years ago by a prominent Western agri- 
cultural newspaper, TJie Farmers'' Review, to 
estimate approximately the pecuniary loss 



from the attacks of a single one of these 
insects — the ox hot fly, or ox warble — on 
the cattle received at the Union Stock 
Yards, of Chicago. It was estimated that 
50 per cent, of the cattle received each year 
are affected. The number of cattle received 
at the yards during six months of the year 
1889 was 1,335,026; the average value of 
the hide was |3,90 ; the usual deduction for 
hides damaged by the ox warble was one- 
third. Estimating at less than one-third, say 
$1.00, the actual loss during six months on 
hides alone was $667,513. When to this 
was added the loss for depreciation in value 
and lessened quantity of beef, the loss for 
-each infested animal v/as put at $5.00, a 
very low estimate, indicating the total loss 
from the animals in the Union Stock Yards, 
of Chicago, for a period of six months of 
$3,336,565. 

AS ANNOYING MAN. 

There are very few regions of the habit- 
able globe where man is not personally 
subject to more or less annoyance b}' in- 
sects. In this part of the world we natu- 
rally think at once of mosquitoes, house flies, 
fleas, and of a certain other species which 
it will not be necessary to name. 

A susceptible individual some years ago 
wrote to the Department of Agriculture 
and said that he had come over from the 
old country and settled in New Jersey, but 
that the mosquitoes bothered him so greatly 
that on the advice of friends he moved to 
northern New York. Here he found that 
during a certain portion of the year black 
flies made life unendurable ; thereupon he 
packed his household effects and moved to 
North Carolina. Here, however, in the 



summer months red bugs, or jiggers, both- 
ered him to such an extent that he feared 
he would go crazy, and in this desperate 
condition he applied to this office to learn 
whether there existed in the United States 
a locality where a sensitive individual could 
find peace from attacks of insects. He said 
that he had been told that in the Western 
eountrj^ the buffalo gnat was greatly to be 
feared, while certain other biting flies would 
be sure to keep him in a constant state of 
dermal irritation ; that further south he 
knew that peaceful nights were to be gained 
in the summer time only under the protec- 
tion of mosquito bars. He had thought of 
the newly developing country of Alaska, but 
had recently seen an account in the news- 
paper of the ferocity of the Alaskan mos- 
quitoes, which had practically destroyed his 
last hope. 

Accustomed as most of us are to the mos- 
quitoes of temperate North America, we 
hardly realize the impression which they 
made upon the early English travellers. A 
story told by Kirby and Spence, to the 
effect that Mr. Weld in his travels relates 
from General Washington that in one place 
the mosquitoes were so powerful as to pierce 
through his boots, has always excited my 
interest and curiosity, and I recently took 
the trouble to consult the original publica- 
tion, which is ' Isaac Weld's Travels through 
North America, 1795-1797,' London, 1799. 
In speaking of Skenesborough, in northern 
New York, Mr. Weld dilates upon the 
number and ferocit}^ of the mosquitoes, and 
makes use of the following words: " Gen- 
eral Washington told me that he never was 
so much annoyed by mosquitoes in any 
part of America as in Skenesborough, for 



9 



that they used to bite through the thickest 
boot." ISTow, knowing that the boots of 
those days were very thick and that the 
mosquitoes of that time must have been 
structurally identical with those of to-day, 
there arises instantly a question of veracity 
between Mr, Weld and General Washing- 
ton ; and as we know from Dr. Weems' 
veracious historj' that General Washington 
was so constituted that he could not tell a 
lie, it looks very much as though Mr. Weld, 
like many another English traveller who 
has written a book on his return home, has 
been inclined to overstate the truth. 

In these days of comparative personal 
cleanliness some of the most disgusting of 
the insect annoyers of man have dropped out 
of sight. The lice, which in former days 
were common in all classes of society, from 
king to peasant, are now comparatively un- 
known. The itch disease, which carried off 
many a famous character in history, is 
equally rare. That it still persists, how- 
ever, is shown bj^ an occasional case re- 
ported in medical journals. For example, 
Dr. Robert Hessler, of Indianapolis, re- 
ported in 1892 a case in his own practice 
of typical Norway itch in which the itch 
mites were present in the skin of the patient 
in enormous numbers. A rough estimate 
showed seven million eggs and two million 
mites. 

Those of us who live in a reasonably civil- 
ized way are confined, in our experience of 
annoying insects, largelj^ to the forms men- 
tioned in our opening paragraph, namely, 
mosquitoes and house flies and rarely fleas ; 
but a glance through the medical literature 
reveals the existence of more or less fre- 
quent cases of such a nature that they are 



10 



little less than horrible. Prominent among 
these are the cases of so called Myasis, and 
especially those resulting from the attacks 
of the screw worm fly, Compsomyia macel- 
laria. 

Residents of temperate regions are fortu- 
nate as compared with those of tropical 
regions in respect to the personally annoy- 
ing insects. Our troubles from these indi- 
vidually insignificant causes are intensified 
to a degree in warmer countries, where the 
comfort of the individual absolutely depends 
upon the adoption of measures, always dif- 
ficult and frequently impracticable, to ex- 
elude insects from his person and from his 
food. This is so well known in these days 
of numerous books of travel that I will 
close this aspect of our question simply 
with a quotation from a poet of the Indies^ 
written many years ago : 

" On every dish the booming beetle falls, 

The cockroach plays, or caterpillar crawls : 

A thousand shapes of variegated hues 

Parade the table and inspect the stews. 

To living wal's the swarming hundreds stick, 

Or court, a dainty meal, the oily wick ; 

Heaps over heaps their slimy bodies drench, 

Out go the lamps with suffocating stench. 

When hideous insects every plate defile, 

The laugh how empty, and how forced the smile !'* 

AS CARRIERS OF DISEASE. 

Manson's demonstrated transmission of 
the filaria diseases of the East (elephan- 
tiasis, chyluria and lymph scrotum) by in- 
sects ; the discovery by Salmon and Smith 
of the carriage of the germ of Texas fever 
by the well known Southern cattle tick ; 
the discovery by Koch of the fact that the 
Tsetse fly of Africa is so destructive to 
animals, not by its bite alone, but by carry- 



11 



5ng into the circulation of the animal that 
it attacks the micro-organisms of disease ; 
the demonstration by Howe and others of 
the previously suspected fact that the puru- 
lent conjunctivitis of the Egyptians is spread 
•by the house fly ; the partly proven hypoth- 
esis of Manson and Grassi of the relation 
existing between mosquitoes and malaria; 
the circumstantially proven carriage of the 
germs of Asiatic cholera and typhoid fever 
by flies ; the demonstration claimed by 
Finlay of the carriage of a mild type of 
yellow fever by mosquitoes ; the suggestion 
by Hubbard that the ' pink eye ' of the 
South is spread by Hippelates; the well- 
recognized fact among the Europeans of the 
Fiji Islands that without a veil a serious 
native eye disease will spread through the 
medium of gnats ; the suggestion by Symond 
of the agency of fleas in the spread of 
the bubonic plague ; the demonstration of 
anthrax bacilli in malignant pustules in 
human beings, caused by the bite of Taba- 
nus and Stomoxys — all indicate an impor- 
tant and very injurious function of insects 
practically unsuspected until comparatively 
recent years. It is, in fact, a rapidly in- 
creasing field of investigations, the possi- 
bilities of which cannot be accurately estab- 
lished at the present time. It is, however, 
not a field which should be left entirely to 
the medical bacteriologist ; the entomolo- 
gist should have a share. The life histories 
and habits of the insects concerued in the 
damage should be thoroughly understood, 
since it is not impossible that otherwise the 
medical investigators may find themselves 
arriving at perhaps unwarranted conclu- 
sions. For example, it is a fact probably 
unknown to the medical men who may be 



12 



strongly impressed by the suggested car- 
riage of tj'^phoid germs by flies, that the 
house fly, so common in our dining rooms, 
does not breed in and rarely visits human 
excrement, while those other kinds of flies, 
which do so breed, are rarely attracted to 
articles of food used by human beings. In 
the crowded and unnatural conditions of 
army camps, however, and especially where 
cavalry regiments are stationed, so that 
there are great amounts of horse manure, 
the house fly may breed in such enormous 
numbers as to render of verj likely occur- 
rence a departure from the normal food 
habits of the adult. 

Enough has been shown, however, to em- 
phasize the potentiality of this phase of 
insect injury. 

BENEFITS 
AS DESTROYERS OF INJURIOUS INSECTS. 

The economic bearings of insect enemies 
of insects are very great, and perhaps this 
is, all things considered, the most important 
of the beneficial function of insects as a 
class. 

In the eternal warfare of organism upon 
organism, in the perpetual strife of species, 
one preying upon another and that upon a 
third, the complications of relations of 
forms which determine the abundance of 
one species and the scarcity of another are 
nowhere more marked than among the in- 
sects. In fact, to the student of insects who 
has followed out even a single chain of these 
inter- relationships the thought must neces- 
sarily come that upon its organic environ- 
ment, and especially upon its relations with 
its living neighbors of the animal kingdom, 
depend the chances of a species not only for 



13 



increase, but for survival almost to no lesser 
degree than upon its inorganic environment. 
Temperature is the great factor which con- 
trols the geographical distribution of life, 
and temperature ia at the back of all these 
apparent living first causes which control 
the abundance of a species in a given region, 
provided we trace them far enough. Yet 
these living causes, themselves aifected bj' 
other living causes in an almost endless 
chain, sometimes, to all appearance, dwarf 
even temperature as a controlling factor. 

There is not a species of insect that has 
not its natural enemies in the guise of other 
insects; there is not one of these other in- 
sects which has not its own insect foes. 
From a single species of Bombycid moth, 
the larvae of which frequently damage 
forests in Europe to an alarming extent, 
there have been reared no less than sixty 
species of hymenopterous parasites. From a 
single caterpillar of Plusia brassicce have been 
reared 2,528 individuals of a little hymen- 
opterous parasite, Cojndosoma truncatellum.-^ 

Outbreaks of injurious insects are fre- 
quently stopped as though by magic by the 
work of insect enemies of the species. 
Hubbard found, in 1880, tliat a minute par- 
asite, Tricliogramma pretiosa, alone and un- 
aided, almost annihilated the fifth brood of 
the cotton worm in Florida, fully ninety 
per cent, of the eggs of this prolific crop 
enemy being infested by the parasite. Not 
longer ago than 1895, in the city of Wash- 

* Tliis observation, which for some years 'held the 
record, ' as the expression is, was made by Mr. Per- 
gande, of the U. S. Department of Agriculture. Re- 
cently, however, Professor A. Giard, of Paris, has 
more than 3,000 specimens of the same parasite reared 
from a Plusia caterpillar. 



14 



ington, more than ninety-seven per cent, of 
the caterpillars of one of our most important 
shade- tree pests were destro3'ed by para- 
sitic insects, tothe complete relief of the city 
the following year. The Hessian fly, that 
destructive enemy to wheat crops in the 
United States, is practically unconsidered 
by the wheat growers of certain States, for 
the reason that whenever its numbers be- 
gin to be injuriously great its parasites in- 
crease to such a degree as to prevent ap- 
preciable damage. 

The control of a plant-feeding insect by 
its insect enemies is an extremely compli- 
cated matter, since, as we have already- 
hinted, the parasites of the parasites play 
an important part. The undue multiplica- 
tion of a vegetable feeder is followed by 
the undue multiplication of parasites, and 
their increase is followed by the increase of 
hyper parasites. Following the very in- 
stance of the multiplication of the shade- 
tree caterpillar just mentioned, the writer 
was able to determine this parasitic chain 
during the next season down to quaternary 
parasitism. Beyond this point, true internal 
parasitism probably did not exist, but even 
these quaternary parasites were subject to 
bacterial or fungus disease and to the at- 
tacks of predatory insects. 

The prime cause of the abundance or 
scarcity of a leaf-feeding species is, there- 
fore, obscure, since it is hindered by an 
abundance of primary parasites, favored by 
an abundance of secondary parasites (since 
these will destroj'^ the primary parasites), 
hindered again by an abundance of tertiary 
parasites, and favored again by an abun- 
dance of quaternary parasites. 

The subject of practical handling of in- 



15 



«ect enemies of insects has come into great 
prominence during the past ten years. The 
suggestion by the Rev. Dr. Bethune, of 
Canada, many years ago, of the desirability 
of importing the European parasite of the 
wheat midge into America was probably 
the first published international suggestion 
of this nature, and, although some subse- 
quent correspondence between English and 
American entomologists ensued, no parasites 
were actually sent over. Later, attempts 
were made by LeBaron in the case of a 
parasite of the oyster-shell bark-louse of 
the apple, and by Professor Riley in the 
case of a parasite of the plum curculio, to 
transport parasites from one section of the 
United States to another, both attempts 
meeting with some slight success. 

In 1873 Planchon and Riley introduced 
an American predatory mite, which feeds 
in this country on the grape vine Phylloxera^ 
into France, where it became established, 
but where it accomplished no appreciable 
results in the way of checking the spread of 
this famous vine pest. 

In 1874 efforts were made to send certain 
parasites of plant-lice from England to New 
Zealand, without recorded results of value. 

In 1880, in an article upon the para- 
sites of American scale insects, the writer 
showed that international transportation is 
especially easy, and especially des^irable in 
the case of these insects. 

In 1883 Dr. Riley succeeded in importing 
a common European parasite of the im- 
ported cabbage worm into tlvis country, 
where it established itself and has since 
proved to be a valuable addition to our fauna. 

In 1891 the same distinguished entomol- 
ogist brought about the importation of one 



16 



of the European parasites of the Hessian 
fly through the assistance of Mr. Fred. 
Enock, of London. This parasite main- 
tained itself in this country certainly a& 
late as 1895, but has accomplished no ap- 
preciable good, so far as has been ascertained, 
in limiting the increase of this destructive 
enemy to wheat. 

All previous experiments of this nature 
were dwarfed into insignificance by the as- 
tounding success of the importation of Novms 
( Vedalia) cardinalh, a ladybird beetle, from 
Australia into California in 1S89. This 
importation was made, as will be remem- 
bered, by Mr. Albert Koebele, an attache 
of the Division of Entomology of the United 
States Department of Agriculture, whose ex- 
penses, however, were paid out of a fund 
appropriated to the Department of State, 
for the purpose of securing a representation 
Iroui this country at the Melbourne Expo- 
sition. A California man, the late Mr. 
Frank McCoppin, happened to be at the 
liead of the Exposition Commission ; and, 
while the late Dr. C. V. Riley was endeav- 
oring in Washington to induce the Depart- 
ment of State to set aside a sum, from the 
Exposition fund, for the expenses of Mr. 
Koebele, representatives of the State Board 
of Horticultui-e of California were pressing 
the same facts upon Mr. McCoppin, the 
head of the Commissioa. These efforts 
were being made independently and with- 
out considtation, hence it happened that 
after Mr. Koebele had succeeded in sending 
live Vedalias to California, and after these 
insects, by their rapid multiplication and 
voracious habits, had absolutely destroyed 
the cottony cushion scale in the orange 
groves of the State, a result which prac - 



17 



tically saved millions of dollars to Califor- 
nia, and which attracted the attention of 
everyone interested in science or agricul- 
ture, a most unfortunate controversy en- 
sued between Dr. Riley and the California 
State Board of Horticulture as to the placing 
of the credit of carrying out this wonder- 
fully successful experiment. This contro- 
versy embittered the last days of both Dr. 
Riley and Mr. McCoppin, and was the cause 
of a disturbance of the formerly pleasant 
relations between the United States Depart- 
ment of Agriculture and the State Board of 
Horticulture of California, which has only 
recently been overcome. 

Following this successful experiment, the 
same insect, Noviiis cardinalis, was sent to 
South Africa, where it exterminated the 
white or fluted scale in that colony. The 
next year it was sent to Egypt, where it 
exterminated a congeneric scale insect in 
the gardens of Alexandria. 

The following year Mr. Koebele, still an 
agent of the United States Department of 
Agriculture, was sent with the consent of 
the Honorable Jeremiah Rusk, but at the 
expense of the California State Board of 
Horticulture, to Australia, New Zealand 
and the Fiji Islands, for the purpose of 
securing other valuable beneficial insects 
for importation into California. Thousands 
of such insects, comprising a number of 
different species, nearly all, however, of 
them Coccinellids, or ladybirds, were sent 
over and established in California. Several 
of these species are still living in different 
parts of the State. The overwhelming suc- 
cess of the importation of Novius cardinalis 
was not repeated, but one of the insects 
brought over at that time, namely, Rhizobius 



IS 



venfralis, has unquestionably ridden many 
olive groves of the destructive black scale^ 
and is to-day present in many other orchards 
in such numbers that the scale practically 
makes no headway. 

After this second Oriental trip the rela- 
tions between the Department of Agricul- 
ture and the State Board of Horticulture of 
California became so strained that the Cali- 
fornia agents of the Department were given 
their choice by the Honorable Secretary of 
Agriculture to resign their positions or be 
transferred to Washington. Mr. Koebele 
resigned and w^as soon after employed by 
the then newly established Hawaiian Re- 
public for the purpose of travelling in dif- 
ferent countries and collecting beneficial 
insects to be introduced into Hawaii for the 
purpose of destroying injurious insects. It 
is difficult at this time to ascertain the 
exact results of the more recent portion of 
this work. Mr. Koebele's own published 
reports have dealt less with results than 
with the details of the introduction of in- 
sects, and anonymous newspaper reports 
are not to be accepted as scientific evidence. 
Fortunately, however, one of the collectors 
of the British Association for the Advance- 
ment of Science, Mr. R. E. C. Perkins, was 
in Hawaii during 189(5 and made a report 
on Mr. Koebele's work to the committee ap 
pointed by the Royal Society and the Brit- 
ish Association for investigating the fauna 
of the Sandwich Islands, which was pub- 
lished in Nature for March 25, 1897. From 
this report it appears that the introduction 
of Coccinella repanda from Ceylon, Australia 
and China was so successful in the extermi- 
nation of plant-lice upon sugar cane and 
other crops as to obviate all necessity for 



19 



spraying. The introduction of Crypiolmnus 
montrouzieri from Australia resulted in the 
entire recovery of the coflfee plants and 
other trees which were on the point of be- 
ing totally destroyed by the scale insect 
known as Pulvinaria psidii. Eight other 
introduced species had at the date of writ- 
ing (November, 1896) been entirely natu- 
ralized and were reported as doing good 
work against certain scale insects. A Chal- 
cis fly, Chalcis obscurata, introduced from 
China and Japan, multiplied enormously at 
the expense of an injurious caterpillar 
which had severely attacked banana and 
palm trees. Mr. Koebele, when visiting 
Washington during November, 1898, men- 
tioned a number of other importations of 
beneficial insects into Hawaii, about which 
it is as yet too early to speak. 

A very recent instance of an international 
importation of striking value is the sending 
of Novms cardinalis from this country to 
Portugal, where the white or fluted scale 
has been checked and in many orchards ex- 
terminated in the course of a single year. 
This importation was made by the writer 
with the invaluable assistance of the Cali- 
fornia State Board of Horticulture. 

Other experiments in this line are under 
way. A parasite of certain wax scales, 
which are abundant and injurious in the 
South, has been imported by the writer 
from Italy, with the cooperation of Pro- 
fessor Antonio Berlese, of the Royal Scuola 
di Agricoltura di Portici ; while an effort is 
being made to bring from Europe insects 
which will prey upon the Gipsy moth which 
has been so great a plague about Boston ; 
and other parasites of injurious scale insects 
in foreign countries are being studied with 



20 



the purpose of eventual]}' obtaining their 
introduction into the United States. 

AS DESTROYERS OF NOXIOUS PLANTS. 

Just as we have shown how important is 
the role played bj'^ insects in the destruction 
of cultivated and useful plants, it will be 
easy to indicate their importance as de- 
stroyers of weeds and other noxious plants. 
We need only mention the common and 
cosmopolitan thistle butterfly {Pijrameis car- 
dui)^ the equally common milkweed butter- 
fly {Anosia plexippus), the purslane cater- 
pillar ( Copidryas gloveri) , the burdock beetle 
( Gastroidea c?/awea), and the purslane sphinx 
moth (Deilephila lineata) to recall to the 
mind of the experienced entomologist many 
other species which do similar work. They 
are here, as in the former case, perhaps the 
principal agents in preventing the undue 
increase of any one species of plant, but as 
we find here not an effort of man to combat 
Nature, as it were, by increasing the growth 
and spread of one species at the expense of 
the others, but the exact opposite, so, here 
also, to a degree we find Nature arrayed 
against man, and insects thus play by no 
means the same part in the destruction of 
weeds that they do in the destruction of 
cultivated crops. Nevertheless, they have 
an important function in this direction, and 
it is safe to say that the benefit which the 
agriculturist derives from their work in this 
way is very great. As long ago as the be- 
ginning of the century it was pointed out by 
Sparrman that a region in Africa, which 
had been choked up by shrubs, perennial 
plants and hard, half-withered and unpal- 
atable grasses, after being made bare by a 
visitation of destructive grasshoppers, soon 



21 



appeared in a far more beautiful dress, 
clothed with new herbs, superb lilies and 
fresh annual grasses, affording delicious 
herbage for the wild cattle and game. 

In a similar way Riley has called atten- 
tion to the fact that after the great grass- 
hopper invasions of Colorado and other 
Western States in the years 1874 to 1876 
there were wonderful changes in the char- 
acter of the vegetation, the grasshopper dev- 
astations being followed by a great preva- 
lence of plants which in ordinary seasons 
were scarcely noticed. It is true that some 
of these plants were dangerous weeds, but 
others were most valuable as forage for the 
half starved live stock. Moreover, other 
plants, and especially short or recumbent 
grasses, took on a new habit and grew lux- 
uriantly ; one species, for example, Eragrostis 
poceoides, ordinarily recumbent and scarcely 
noted, grew in profusion to a height of three 
and a-half feet. 

An important, but not generally realized, 
benefit which is derived from the insects 
maj^ be mentioned under this head, though 
not strictly belonging here. Kirby showed, 
75 years ago, that the insects that attacked 
the roots of grasses, such as wireworms, 
white grubs, etc., in ordinary seasons only 
devour so much as is necessary to make 
room for fresh shoots and the product 
of new herbage, in this manner maintain- 
ing a constant succession of young plants 
and causing an annual though partial reno- 
vation of our meadows and pastures, " so 
that, when in moderate numbers, these in- 
sects do no more harm to the grass than 
would the sharp-toothed harrows which it 
has sometimes been obliged to appl}' to hide- 
bound pastures, and the beneficial operation 



22 



of which in loosening the subsoil these in- 
sect borers closely imitate." 

AS POLLENIZERS OF PLANTS. 

It can no longer he doubted that cross 
fertilization is one of the very most impor- 
tant elements in the progressive develop- 
ment and continued health of the great 
majority of flowering plants, and, indeed, 
that it is with some almost a condition of 
existence. Opposition to this view, at no 
time especially strong since the publication 
of Darwin's great work, has become feebler 
and more feeble until at the present it is 
not worth considering. 

Comparative experimentation with self- 
fertilizing and cross-fertilizing plants, re- 
peated with many species and genera, have 
shown a superior growth and vitality on 
the part of those subjected to cross fertili- 
zation of such a degree as to leave not a 
semblance of a doubt ; while in individual 
cases self fertilization has been scientifically 
shown to even result in a deterioration so 
marked that it has been compared to poi- 
soning. 

In this condition of affairs it at once be- 
comes evident that the good offices of in- 
sects in this direction are of incalculable 
importance, since it must be plain that of 
the natural agencies by which cross- fertili- 
zation of plants is accomplished insects are 
far and away the most prominent. Every 
investigation which has been undertaken 
of recent years, and activity in this field is 
increasing by leaps and bounds, has shown 
the most marvelous adaptations between 
the structure of flowers and the structure 
of their insect visitants, all in the line of 
facilitating or really enforcing the collect- 



23 



ing and carriage of pollen bj^ flower- visiting 
Insects from one plant to another. An esti- 
mate of the numbers of the species of insects 
engaged in this work would include the 
forms belonging to whole families and al- 
most orders, and if we could imagine the 
race of flower- visiting insects wiped out of 
existence the disastrous effect upon plant 
growth would he beyond estimate. I am 
not prepared to state that insects benefit 
plants in this way to such an extent as to 
overcome the results of the work of the 
plant- destroying species, but if it were pos- 
sible to compare in any way the results of 
these two classes of work it is safe to say 
that the effect would be surprising. 

We must, therefore, without going further 
into detail, placf> this pollenization of plants 
as one of the very most important beneficial 
functions of insects in their relations to 
man. 

AS SCAVENGERS. 

Another beneficial function of insects, the 
importance of which can hardly be overesti- 
mated, is their value to humanity in doing 
away with, and rendering innocuous, dead 
matter of both plant and animal origin. 
This subject has never been discussed with- 
out reference to the famous statement by 
Linnaeus that the offspring of three blow- 
flies would destroy the carcass of a horse 
as quickly as would a lion ; and while the 
exact statement in its details is open to 
doubt, still it serves to illustrate, in a strik- 
ing way, the good ofiices of insects, and it is 
certainly true that after the offspring of the 
blow- fly have finished with the horse's car- 
cass this would be left in a much less offen- 
sive condition than after the departure of 
the lion. 



24 



There are inhabited regions in which the 
climate is so dry that dead bodies of ani- 
mals never become offensive, but, by natural 
mummification, remain simplj^ as cumberers 
of the earth. In such regions insects play 
little part. Wherever, however, there is 
sufficient moisture to produce a natural de- 
cay, there insects occur in swarms and 
hasten the destruction of the decomposing 
mass in a marked degree. Were the bodies 
of dead animals not destroyed by insects in 
this way, and, still more, were the destruc- 
tion of dead vegetation not hastened as it 
is by the attacks of countless insects, it is 
perfectly easy to see that the earth would 
not be inhabitable, its surface would be 
covered with the indestructible remains of 
what was once life in some form. 

Large groups of insects, comprising many 
thousands of species, take part in this in 
estimable work, and it will probably be un- 
necessary in order to bring about a realiza- 
tion of this value to dwell further upon the 
subject. 

AS MAKERS OF SOIL. 

It is a, fact not generally realized that 
insects must take an important part in the 
changes in the character of the soil which 
are constantly going on. Occurring in such 
countless millions, as they do, constantly 
penetrating the soil in all directions, fre- 
quently dragging vegetation below the sur- 
face and bringing the subsoil up to the 
surface, changing the character of the soil 
humus by passing it through their bodies, 
and fertilizing the earth by their own death 
and decay, it is probable that insects are 
responsible for even more soil change than 
are the earth worms, which Darwin has 
placed before us in such an important light. 



25 



Insects are found beneath the ground in 
incredible numbers ; some of them pass 
their whole life underground, feeding upon 
roots and rootlets, upon dead and decaying 
vegetable matter, upon soil humus and 
upon other insects; many of them have 
their nests underground, although they get 
their food elsewhere ; while others hide 
their eggs or pupse underground. 

The depth to which they penetrate is 
something surprising ; the minute insects 
of the family Poduridse have been found 
swarming literally by the million at a depth 
of six to eight feet in a stiff clay subsoil. 

AS FOOD AND CLOTHING AND AS USED IN THE 
ARTS. 

In this role insects play an important 
part. Insects as food, and their products 
as clothing, are well known to all. The 
great silk industry of the world is derived 
wholly from insects, and almost entirely 
from a single species, the silkworm of com- 
merce. 

As food, insects have formed articles of 
diet for certain savage peoples since the 
beginning of the human race. Hope, in 
1842, catalogued forty-six species of insects 
used as food, and Wallace, in 1854, showed 
that insects of six different Orders were used 
as food bj" the Indians of the Amazon. 
Semi-civilized peoples to-day use certain in- 
sects as food, as witness the consumption 
of Corixa eggs by the Mexicans, and a book 
has been written under the caption ' Why 
not eat insects ? ' for the purpose of show- 
ing that many possibilities in the way of 
dietetics are being ignored to- day. M. de 
Fontvielle, in addressing the Societe d'ln- 
sectologie, in 1883, expressed regret that the 



26 



attempts made to popularize the use of in- 
sects as food have made so little progress, 
and said that we ought not to forget the 
remark of the Roman Emperor who said 
that the body of an enemy never tasted 
bad, and that the banquet of the Society 
would always lack something so long as 
there was not placed before them at least 
some grasshopper farina and fried white 
worms. 

A single insect, the honey bee, furnishes 
a notable article of food, and is the basis of 
a great and world-wide industry. 

As food for poultry, song birds and food 
fish, insects are indirectly of great benefit 
to man. Not only do they provide living 
food for such animals, but Corixa mercenarm^ 
a water bug, is now being imported by the 
ton from Mexico into England as food for 
birds, poultry, game and fish. One ton of 
these bugs has been computed by Mr. G. 
W. Kirkaldy to contain 250,000,000 of in- 
sects (Entomologists' Monthly Magazine^ Au- 
gust, 1898). 

In the days of pure empiricism in medi- 
cine, insects were used extensively, and we 
have only to mention the Spanish fly to 
show that they are still of some value. 

In the arts, shellac and Chinese white 
wax, as is well known, are insect products, 
as also are the formerly greatly used coch- 
ineal dye and Polish berry dye, the so-called 
berry in this case being an insect and not a 
berry. 

The last-named instances are all derived 
from scale insects, a group of astonishing 
capacity for multiplication, the commercial 
possibilities of which are by no means ex- 
hausted, as I took pleasure in showing in a 
paper read before the Amer-ican Association 



27 



for the Advancement of Science in 1897. It 
should be noted here, also, that there is 
good reason to believe that the manna of 
the Bible, upon which the Children of Israel 
subsisted while in the Wilderness, was also 
the secretion of a scale insect. 

SUMMARY OF THE HABITS OF INSECTS. 

After this general account, arranged under 
the classes of damage and classes of benefits 
brought about by insects, it will be well to 
attempt an arrangement of the subject in a 
somewhat different manner, in order to gain, 
if possible, some light as to the relative 
proportion of insects which are injurious or 
beneficial. 

It will be manifestly impossible to cata- 
logue the species or the genera in this way, 
and it will be obvious that a classification 
from families will be lacking in exactness, 
since some of the families are very large in 
number of species and others exceedingly 
small ; but, taking the groups as a whole, 
no better and speedier means suggests itself 
than to summarize the habits by families. 

Another difficulty, however, which arises 
in such a classification is the fact that some 
orders are in a much more advanced stage 
of classification than others, and the force 
which is given to a familj' as a taxonomic 
group varies with the views of the latest 
monographer. Nevertheless, taking only 
the older and generally accepted families 
and analyzing habits, we find the situation 
to be as follows : 

Of 33 families of Hymenoptera, but two 
are strictly plant- feeding; the Cynipidaj, or 
gall flies, are in the main injurious to 
plants, but some forms are parasitic ; nine 
families are strictly parasitic upon other 



2S 

insects ; fifteen are predatory upon other 
insects ; two, comprising the bees, have no 
other especial value in their relations with 
man than as pollenizers of plants, or pro- 
ducers of honey ; three, comprising the ants, 
are beneficial as scavengers, but injurious 
in their other relations. It must be re- 
membered, however, that at least 27 of the 
33 families are of the greatest value in the 
cross- fertilization of plants, in which work 
the insects of this order perhaps take the 
lead. 

In the Coleoptera, or beetles, considering 
82 families, the insects of nine families on 
the whole are injurious, and of 23 families 
on the whole are beneficial aa destroying 
injurious insects ; 10 families are beneficial 
as scavengers, and 30, or more, mostly small 
groups of little importance, contain some 
scavengers and many neutral forms of prac- 
tically no economic importance, although 
certain of them visit flowers ; two families 
contain both injurious and beneficial forms, 
as well as manj^ that are neutral. 

In the Siphonaptera, or fleas, the species 
of the single family are parasitic upon 
warm-blooded animals. 

In the Diptera, or true flies, if we classify 
the families according to habits of the 
majority of the species in each, we get ap- 
proximately : injurious families, 10; preda- 
ceous families, 11; parasitic family, 1 ; scav- 
engers, 19. In point of numbers, of indi- 
viduals in this order, as well as in the 
Coleoptera, no doubt the injurious will ex- 
ceed the predaceous ; while in the Diptera 
the scavengers will probably equal all of 
the others put together. 

In the Lepidoptera practically all of the 
60 odd families are injurious through the 



29 



damage done by their larvse to vegetation, 
but here again it must be remembered — and 
the same comment holds for many of the 
Diptera which we have just considered — that 
the adult insects are among the most active 
and frequent visitors of flowers and have a 
great and beneficial effect on cross- fertiliza- 
tion. 

In the Trichoptera the insects of the 
single family feed upon aquatic plants and 
have no economic value except as furnish- 
ing food for food fishes. 

The insects of the single family in the 
order Mecoptera are indifferent in their 
economic relations, though probably slightly 
beneficial. 

In the Neuroptera all of the seven fami- 
lies are beneficial through their predaceous 
habits, with the exception of the Sialidse, 
which, since their larvte are aquatic, may 
be termed indifferent or neutral, though it 
has both a beneficial and an injurious rela- 
tion to food fishes. 

In the Homoptei-a we have nine families, 
all of which are injurious except that here 
and there a species has had a commercial 
value, like the lac and dye insects. 

In the Heteroptera there are 11 fami- 
lies which are strictly plant feeders ; 8 are 
strictly predaceous ; 3 are both injurious 
and predaceous; while the economic value 
of 13 is more or less doubtful. Most of 
these last are aquatic and have some value 
as fish food. 

The insects of the single family of the 
order Physaptera are injurious. 

In the Orthoptera we have one family of 
strictly predaceous habits ; one which has 
a mixed food and is partly injurious and 
partly beneficial as its species become scav- 



30 



eugers ; the habits of 1 family are unknown; 
while in the 4 remaining families the species 
are all injurious as destroyers of vegetation. 

The insects of the single family of the 
order Euplexoptera are probably beneficial 
as predatory forms and scavengers. 

The single family of the order Malloph- 
aga is injurious, containing parasites oi 
birds and mammals. 

In the Corrodentia the habits of the in- 
sects of the single famil}' are on the whole 
of little economic importance, though the 
species are to be classified in the main as 
scavengers. 

In the Isoptera the forms belonging to 
the two families are injurious. 

In the Order Plecoptera the species of 
the single family are practically neutral in 
their economic relations, although they 
possess some value as fish food. 

All of the insects of the single family of 
the order Odonata may be called beneficial ; 
the adults are predaceous upon other in- 
sects and are thus strictly beneficial, but the 
larvae may in a sense be termed injurious, 
since they are aquatic and prey upon other 
aquatic insects w^iich themselves may be 
food for fishes. 

The insects of the single family of the 
order Ephemerida are of little economic 
value, except that they are important fish 
food. 

Lastly, the insects of eight of the fami- 
lies of Thysanura are beneficial as scaven- 
gers and soil markers, while some of the 
species of one family are somewhat harmful 
from the damage which they do in house- 
holds. 

Tabulating the facts thus gained we have 
the following : 



31 



Injurious as feeding upon cultivated and 
useful plants, the insects of 112 families. 

Injurious as parasitic upon warm-blooded 
animals, the insects of 1 family. 

Beueficial as preying upon other insects, 
the insects of 79 families. 

Beneficial as scavengers, the insects of 32 
families. 

Beneficial as pollenizers only, the insects 
of 2 families. 

Beneficial as forming food for food fishes, 
the insects of 3 families. 

Of undetermined economic importance, 
the insects of 49 families. 

Families containing both injurious and 
beneficial forms, 22. 

The totals are : 

Beneficial, the insects of 113 families. 

Injurious, the insects of 116 families. 

Both, or undetermined, the insects of 71 
families. 

CONCLUSION. 

And now the question is: Are we any 
nearer the answer of the query in the title 
of this paper than we were at the start? 
We have, perhaps, gained by this summary 
a clearer idea of the economic importance 
of the class Insecta, and possibly it may 
appear by this contrasting method that the 
benefits derived from insects entirely ofiset 
their injuries ; but we cannot, in our present 
stage of enlightenment (and I say it with all 
reverence), complacently and piously adopt, 
with the good old I'ector of Barham, the 
view that insects, with all the lower ani- 
mals, were created for man's benefit, God 
permitting occasional injuries, to use Kirby's 
words, " not merely with punitive views, but 
also to show us what mighty effects he can 
produce by instruments so insignificant. 



32 



thus calling on us to glorify his power, 
wisdom and goodness." 

Contrast with this view the view of Pro- 
fessor Bailey, in one of his charming essaj'S 
in the volume entitled ' The Survival of the 
Unlike :' " We are now prepared to admit 
that this whole question of enemy and 
friend is a relative one, and does not depend 
upon right and wrong, but simply upon our 
own relationships to the given animals and 
plants. An insect which eats our potatoes 
is an enemy because we want the potatoes 
too ; the insect has as much right to the 
potatoes as we have. He is pressed by the 
common necessit}' of maintaining himself, 
and there is every evidence that the potato 
was made as much for the insect as for the 
human kind. Dame Nature is quite as much 
interested in the insect as in man. ' What 
a pretty bug!' she exclaims ; ' send him 
over to Smith's potato patch.' But a bug 
which eats this insect is beneficial ; that is, 
he is beneficial to man, not to the insect. 
Thus everj^thiug in nature is a benefit to 
something and an injury to something; and 
every time that conditions of life are modi- 
fied the relationships readjust themselves." 

In these w^ords Bailey, with his accustomed 
felicity, has expressed the situation admi- 
rably. Man is but one of the forms of life 
struggling for existence, at continual war- 
fare with surrounding forms ; but by virtue 
of his surpassing intelligence — itself as grad- 
ually evolved as have been the physical 
characteristics of any given species — he has 
overrun the earth, has accommodated him- 
self to the most unnatural environments ; 
he has dominated all other species in na- 
ture ; he has turned to his own uses and 
encouraged or hastened the evolution of 



33 

species useful to him or of useful qualities 
in such species ; he has wiped out of exist- 
ence certain inimical forms, and is gaining 
the control of others. He is the dominant 
type, and types whose existence and methods 
of life are opposed to his interests are being 
pushed to the wall. It is the culmination 
of a history which has many times repeated 
itself in past ages. The struggle of other 
forms of life to accommodate themselves to 
the conditions brought about by the rapid 
development of this dominant type is one 
the most interesting fields of study open to 
the biologist to-day. It would seem as if, 
in man's efforts to make the face of the 
earth his own, all the complicated elements 
of life were arrayed against him, and the 
great and ultimate result of the labor of the 
biologist in his study of the relations of the 
different forms of life and the laws which 
govern their development will be to bring 
about the absolute control of all other life 
by man. Thus it is not only the economic 
worker who looks for immediate results of a 
practical kind from his labor — the scientific 
agriculturist, the horticulturist, the eco- 
nomic zoologist, the medical bacteriologist 
— who should command the respect of even 
the practical- minded man, but the biologist 
in whatever field, however restricted it 
may be, whether he is working towards the 
understanding of broad principles and gen- 
eral laws, or whether in some narrow corner 
of research, he is accumulating material 
which will help ultimately to lead to wider 
understandings — all are working helpfully 
and practically towards the perfect well- 
being of the human race. 

L. O. Howard. 
Washington, D. C. 



015 793 727 3 • 




